Conventionally, coating films composed of a polyimide resin having combined excellent heat resistance, electrical properties and mechanical properties have been widely used for insulating materials of electronic parts and surface protection films, interlayer insulating films and α-ray shielding films in semiconductor devices.
For forming such polyimide resin coating films, a non-photosensitive polyimide resin precursor composition or a photosensitive polyimide resin precursor composition may be used. By applying a material provided in the latter form on a substrate, exposing the material to an active light through a desired patterning mask, developing it and then heating it, a cured relief pattern layer formed from a polyimide resin having heat resistance can be more easily formed.
Accordingly, when a polyimide resin is used as a coating film for which no cured relief pattern needs to be formed, the polyimide resin precursor composition may be non-photosensitive or photosensitive. However, when a polyimide resin is used for manufacturing a semiconductor device comprising a cured relief pattern layer formed from the polyimide resin, photosensitive polyimide resin precursor compositions have an advantage over non-photosensitive polyimide resin precursor compositions in that production steps can be significantly reduced.
When photosensitive polyimide resin precursor compositions have been first used, exposure to g-line (wavelength: 436 nm) from a ultra-high pressure mercury lamp has been generally performed, but now exposure to i-line (wavelength: 365 nm) having a higher resolution is general. Photosensitive polyimide resin precursor compositions with high i-line transmittance are preferred as a composition used for i-line exposure. A composition comprising a polyimide resin precursor obtained by condensing diphenyl ether-3,3′,4,4′-tetracarboxylic acid and a diamine compound and the like are proposed (see, for example, JP-A-6-342211).
Recently, methods of mounting semiconductor devices on printed wiring boards have been shifting from conventional mounting methods using metal pins and tin—lead eutectic soldering to methods comprising bringing a polyimide resin coating film into direct contact with solder bumps, such as CSP (chip size packaging), which enable higher density mounting. In other words, polyimide resin coating films have come into contact with flux in the solder bump reflow process, requiring even higher heat resistance.
Also, in the steps of manufacturing semiconductor devices, there are many attempts to increase the diameter of a silicon wafer which is a substrate to 300 mm for high efficiency and lowering of the cost. In the process of applying a photosensitive polyimide resin precursor composition to a silicon wafer and forming it into a polyimide resin coating film by heating, the silicon wafer is warped due to residual stress. Thus, since polyimide resin coating films have begun to be used for silicon wafers with a larger diameter, further reduction of residual stress is now required.
However, generally many polyimide resin coating films obtained from aforementioned composition for i-line exposure have a lower glass transition temperature and higher residual stress than polyimide resin coating films obtained from a composition for g-line exposure. Thus, various methods for improving the heat resistance, typically the glass transition temperature, of a polyimide resin coating film are proposed. For example, a composition obtained by adding a melamine resin to a photosensitive polyimide resin precursor composition is proposed (see International Publication No. WO2004/008252). Various methods for reducing residual stress of polyimide resin coating films are also proposed. For example, a composition comprising a polyimide resin precursor obtained by condensing a tetracarboxylic acid compound containing a repeating unit composed of siloxane with a diamine compound is proposed (see JP-A-2001-154365).
JP-A-5-27245 discloses a polyamide resin obtained by reacting an acid component having a specific structure such as 5-hydroxyisophthalic acid dodecanoate chloride and an acid component having a specific structure such as terephthalic acid in a specific molar ratio with a diamine component such as diaminodiphenyl ether, and a composition containing the resin. However, the resin is a polyamide used for liquid crystal alignment layers, but not a polyamide for a precursor of heat resistant resins.
As described above, in the technical field of photosensitive polyimide, a method of improving the glass transition temperature of a polyimide resin coating film after curing and a method of improving the glass transition temperature of a polyimide resin coating film after curing with maintaining the low residual stress of the film are required.
Patent Document 1: JP-A-6-342211
Patent Document 2: International Publication No. WO2004/008252
Patent Document 3: JP-A-2001-154365
Patent Document 4: JP-A-5-27245